The subject matter disclosed herein relates to a motion control system with independent carts and a linear drive system. More specifically, a system and method is disclosed for monitoring operation of the independent carts as they travel along the linear drive system.
Motion control systems utilizing movers and linear motors can be used in a wide variety of processes (e.g. packaging, manufacturing, and machining) and can provide an advantage over conventional conveyor belt systems with enhanced flexibility, extremely high-speed movement, and mechanical simplicity. The motion control system includes a set of independently controlled “movers” each supported on a track for motion along the track. The track is made up of a number of track segments that, in turn, hold individually controllable electric coils. Successive activation of the coils establishes a moving electromagnetic field that interacts with the movers and causes the mover to travel along the track. Sensors may be spaced at fixed positions along the track and/or on the movers to provide information about the position and speed of the movers.
Each of the movers may be independently moved and positioned along the track in response to the moving electromagnetic field generated by the coils. In a typical system, the track forms a path, which could be a closed path, over which each mover repeatedly travels. At certain positions along the track other actuators may interact with each mover. For example, the mover may be stopped at a loading station at which a first actuator places a product on the mover. The mover may then be moved along a process segment of the track where various other actuators may fill, machine, position, or otherwise interact with the product on the mover. The mover may be programmed to stop at various locations or to move at a controlled speed past each of the other actuators. After the various processes are performed, the mover may pass or stop at an unloading station at which the product is removed from the mover. The mover then completes a cycle along the path by returning to the loading station to receive another unit of the product.
The track is typically formed of multiple segments. Each segment spans a portion of the distance of the entire track and may have various configurations. For example, the segment may be a straight segment having various lengths. Optionally, the segment may be a curved segment where the measure of the arc formed by the curved segment may be, for example, a forty-five degree (45°) arc or a ninety degree (90°) arc. Still other segments may define a switch to or from a second path along the track. The segments required for any track are selected according to the application requirements.
Control of the movers along the track may occur primarily from a central controller or may be distributed to segment controllers positioned along the track. Selection of a controller is dependent on a number of factors including, for example, the size of the track. In some applications, the track may form a continuous loop extending over a short distance, where a function is performed along one side of the loop and the movers return along the opposite side of the loop. In these applications, it may be desirable to utilize a central controller which controls operation of each of the segments. In other applications, the length of the track may span, for example, an entire warehouse and include multiple paths along which the movers may travel. In these applications, it may be desirable to distribute control of the movers to segment controllers located on each segment of the track.
Regardless of whether the movers are controlled by a central controller, segment controllers, or a combination thereof, it may be desirable to monitor the status of movers as they travel along the track. However, monitoring operation of the movers as they travel across different segments of track is not without certain difficulties. The difficulties are increased when control of the movers is distributed to segment controllers. Each segment controller is responsible for controlling operation of the mover along one segment of the track. The segment controllers, however, are unaware of how the mover operates along any other segment of the track. Historically, monitoring operation of a mover would require each segment controller to repeatedly transmit status of a mover to a central controller as the mover travels along the segment. The central controller, in turn, would be required to receive communications from each of the segment controllers, compile data corresponding to operation of one mover received from each of the segment controllers, and generate a report corresponding to the operation or each mover. As the number of movers and number of segments in the system increase, however, the number of data packets that must be transmitted, similarly increases, using a significant portion of the bandwidth of an industrial network connected between the segment controllers and the central controller.
Thus, it would be desirable to provide an improved system and method for monitoring operation of movers in an independent cart system. It would further be desirable to provide a system which reduces the required communication bandwidth for monitoring operation of movers in a system where control is distributed among multiple controllers spaced along the track.